Standard Deviation by Group

[OwenA]

Hi and thank you in advance,

Big Picture: I need to create a flag that tells me when a value exceeds 95% confidence interval (the accepted tolerance limit in this case). These flags will then be counted and reported about by hierarchical group (city, state, country for example) so individual managers can investigate why those exceed expected parameters. 

Technical Issue: I'm having difficulty calculating the standard deviation by row by hierachy group.  

The formula used in "desired standard deviation" column is stdev.p(if($A:$A=$A2,$B:$B)).

How do I replicate this in Power BI?

Thanks so much for your help.

Owen

P.S. Bonus cool points if your solution can be extended to other math functions. 

[johnt75]

You could create a summary table like

Summary Table =
SUMMARIZECOLUMNS (
    'Table'[Bucket],
    "Average", AVERAGE ( 'Table'[Value] ),
    "Std Dev", STDEV.P ( 'Table'[Value] )
)

and then link that to your main fact table. You would then be able to create columns on your fact table which refer to the summary table, e.g. 

Flag =
IF (
    'Table'[Value]
        > RELATED ( 'Summary Table'[Average] ) + RELATED ( 'Summary Table'[Std dev] ),
    1,
    0
)